Thiophene-2-thiol, reaction with

Pyrrolethiols, readily obtained from the corresponding thiocyanates by reduction or treatment with alkali, rapidly oxidize to the corresponding disulfides. They are converted into thioethers by reaction with alkyl halides in the presence of base. Both furan- and thiophene-thiols exist predominantly as such rather than in tautomeric thione forms. 

The Vilsmeier-Haack reaction of ketones forms chlorovinyl aldehydes, which can add thiols readily. The reaction with a-tetralone gave the chlorovinyl aldehyde (230), and reaction with ethyl thioglycolate in ethanolic ethoxide solution formed the dihydro derivative (231), easily dehydrogenated to naphtho[l,2-6]thiophene-2-carboxylate (73JCS(P1)2956). 

The reaction of thiol 128 with / rt-butyllithium affords two isomeric thiophenes 130 and 131. The latter is probably produced through rearrangement of the carbenoids 129 (Scheme 31) <1995JOC5588>. 

This cubane cluster can be converted back to the original one by reaction with CO (30 atm) to form COS, thus completing a cyclic reaction. Although this pair of reactions indicates the possibility of constructing a catalytic cycle for the HDS of thiophene, the presence of free CO unfortunately inhibits the forward desulfurization reaction and therefore the process cannot be rendered catalytic [68]. The exact mechanism of thiophene HDS by use of these clusters in not clearly understood, mainly because the reaction is fast and no intermediates have been isolated or identified. Nevertheless, Curtis has reported extensive related mechanistic studies on the desulfurization of a variety of thiols and sulfides using the same metal cluster Cp 2Mo2Co2S3(CO)4 and as a result of that, the main reaction pathways for desulfurization of these simpler substrates are now well understood [69],... 

Aminofuran-, -pyrrole-, and -thiophene-3-carboxylates and -3-nitriles such as 58 are obtained in a simple, one-step reaction from a-oxo-alcohols, -amines, and -thiols (57) with methylene-active nitriles.53 Thus ethyl 2-amino-4,5,6,7-tetrahydrobenzo[h]thiophene-3-carboxylate (59) results from cyclohexanone, sulfur, and ethyl cyanoacetate26,53 (Scheme 11). The accessible... 

At variance with the homogeneous reactions with [(TRIPHOS)RhH] in which the base simply accelerates the catalytic process, in the biphase reactions the presence of NaOH is mandatory for catalysis to occur. This is most probably because the concentration of BT in the polar phase is too low to promote effectively the elimination of the thiol product. A similar dependence of the reaction rate on Bronsted bases has been observed for the homogeneous hydrogenolysis of thiophene by TRIPHOS/Rh catalysis, and was attributed to the weak nucleophilic properties of thiophene [7]. 

Macrocyclic Thiophens. - Novel macrocyclic Schiff-bases (161), containing thiophen, have been prepared by the non-template condensation of a,co-amino-ethers with thiophen-2,5-dicarbaldehyde. Silver complexes were prepared and crystal structures were determined both for some macrocycles and for a silver complex. In attempts to prepare bridged thia[17]-annulenes, (162) was prepared through the reaction of 2,5-dichloromethyl-thiophen with p-carboxytoluene-a-thiol. Transformation of the carboxyl groups of (162) into bromomethyl, followed by reaction with sodium sulphide,gave (163). The Wittig reaction of 3,4-diformyl-2,5-dimethylthiophen... 

---